All you have to do is follow the steps!
Think of a number - n
Add 10 - n + 10
Add the number you were thinking of - n + 10 + n
Divide by 2 - (n + 10 + n) / 2
Subtract 5 - ((n + 10 + n) / 2) -5
It may look hard, but its not as hard as you think. All you need to do is follow the steps!
